The objective of this Phase I SBIR is to establish the proof of concept for a device and method that uses unique biometric signatures to provide an objective measure of pain and analgesic effect. Background: The overall prevalence of pain in the United States is substantial with 37% of the adult population experiencing chronic pain. Moreover, the rates of chronic pain are expected to continue to rise over time, consequently adding to the overall health and economic burden on the population. With pain being recognized as the upstream driver of the opioid epidemic, adequately addressing pain and its management will not only mitigate the burden of pain but also contribute to preventing the problems associated with the opioid epidemic. Under the current standard of care, pain assessment is subjective and predicated on a linear intensity scale. It does not reflect the complexity of pain and does little to guide interventions best suited to an individual patient?s pain profile. This application describes the development of a novel platform technology that produces an objective measure of pain which can guide analgesic interventions. The Technology: The AlgometRx device is a platform technology that utilizes proprietary algorithms to provide an objective measure of pain and analgesic effect. The measurement of the pupillary response to low-intensity, non-noxious neuro-specific neurostimulation serves as a biometric that reflects nociceptive processes. The derived pain phenotype reflects the impact of any genetic or environmental modulators of pain sensitivity or analgesic efficacy and reflects a personalized evaluation at the time of the assessment. Observations of pain and drug effect using biometric measures eliminate the subjective nature of pain management. Experimental Approach: This proposal includes two studies using the research prototype to characterize different populations of pain and analgesic effects in a clinical setting. The first study will investigate acute pain patients undergoing opioid therapy. The second study will investigate chronic pain patients who receive other forms of analgesics as well as opioids. The data generated from these studies will inform the ongoing development of algorithms to generate a pain phenotype that informs upon the type of pain, the intervention necessary to mitigate the pain, and ongoing monitoring of the intervention. Aims: 1. To develop a methodology for the use of the PRD induced by non-noxious, neurospecific neurostimulation (n-PRD) as an objective measure of pain intensity and sensitivity. 2. To determine the impact of analgesics on the n-PRD. 3. To assess acceptability and feasibility of the technology.